Means for cutting plates for transformer cores

ABSTRACT

For cutting in sequence from a strip of sheet metal all the plates of a transformer core which are interleaved with separate yoke and leg plates, a number of shears are placed obliquely in relation to the feeding direction of the metal strip to cut off plates from the metal strip, along with a number of punches to make notches in the yoke plates for connection of the central leg to the yoke. A number of stops movable into and out of the path of the strip are provided to stop the strip in proper position before each cutting step.

[ jun. 22, 1974 MEANS FOR CUTTING PLATES FOR TRANSFORMER CORES [75] Inventor: Olle Backlin, Ludvika, Sweden [73] Assignee: Allmann Svenska Elektriska Aktieholaget, Vasteras, Sweden [22] Filed: June 1, 1972 [21] Appl. No.: 258,590

[52] lU.S. Cl 83/406, 29/609, 83/255, 83/268, 83/581 [51] int. Cl B26d 11/00 [58] Field of Search..... 83/255, 256, 268, 269, 404, 83/406, 917, 581, 467; 29/609 7/1969 Richardson 83/517 X 2/1945 Somerville 83/516 X Primary Examiner-J. M. Meister 57 ABSTRACT For cutting in sequence from a strip of sheet metal all the plates of a transformer core which are interleaved with separate yoke and leg plates, a number of shears are placed obliquely in relation to the feeding direction of the metal strip to cut off plates from the metal strip, along with a number of punches to make notches in the yoke plates for connection of the central leg to the yoke. A number of stops movable into and out of the path of the strip are provided to stop the strip in proper position before each cutting step.

5 Claims, 8 Drawing Figures MEANS FOR CUTTING PLATES FOR TRANSFORMER CORES BACKGROUND OF THE INVENTION for each cut. The sheet metal is thuscut to form outer legs. The metal is cut to form the middle leg in a second cutting stage. In yet another cutting stage the metal is cut for the yoke and these plates are provided with notches for the central leg. The use of pivotable shears complicates the cutting procedure since the shears must be turn ei 90 between each cutting action and must stop after completion of the turn in an exact position before cutting can be performed. When small cores with short plates are being cut the sheet metal usually has time to be fed forward before the shears are ready to cut, i.e. the total cutting time is increased because of the time needed for the shears to get into position for cutting.

SUMMARY OF THE INVENTION The present invention relates to a means for cutting in sequence from a strip of sheet material all the plates for a transformer core which are interleaved with separate yoke and leg plates. The invention is characterised in that it comprises a number of shears which are placed obliquely in relation to the feeding direction of the metal strip to cut off the plates from the metal strip, a number of punches to make notches in the yoke plates for the connection of the central leg to the yoke and a number of stops to guide the metal strip forward before each cutting stage.

Since the device according to the invention has stationary shears, i.e. they always operate in the same plane, the cutting can be performed more quickly. The combination of shears, punches for notching the yoke plates and stops to guide the sheet metal forward, makes it possible to cut all the plates for a core in one sequence, as will be explained later.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings,

FIG. 1 shows how the shears, punches and stops of the device are arranged and controlled.

FIG. 2 shows the situation of the metal strip when a yoke plate and a side leg plate are produced.

FIG. 3. shows the situation of the metal strip when another yoke plate and a further side leg plate is produced.

FIG. 4 shows the situation of the metal strip when a central leg plate is cut off from the strip.

FIG. 5 shows the central leg plate ready cut.

FIG. 6 shows a first layer of plates in the core and FIG. 7 shows a second layer of plates.

FIG. 8 shows three stacks of ready cut plates.

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a view from above of a device for cutting sheet metal according to the invention. The metal, which is in strip form having the same width as that of the yoke and legs of the finished core, is fed from the left in the drawings along a guiding edge 1. The device has four shears 2, 3, 4 and 5 which are placed as shown in the drawing and which can be moved up and down for cutting. The shears are set at angles of 45 to the guiding edge. There are also two punches 6 and 7 to produce notches in the yoke plates. There are finally four stops 8, 9, I0 and 11 which can be moved up and down. In their lower position the stops are in contact with the cutting track so that they stop the movement of the sheet metal to the right. As can be seen in FIG. 1 the punch 6 is positioned slightly nearer to the guiding edge 1 than the punch 7 so that it makes a slightly deeper notch than the punch 7.

The two punches 6 and 7 and the stops 9 and 10 are adjustable along the cutting track with the help of an adjustment screw 12. This is joumalled in two bearings 13 and 14 and can be turned in some manner known per se, for example by means of the wheel 15 or with the help of a servo-motor. The adjustment screw has three threads 16, 17 and 18. The threads 16 and 17 have the same pitch but are oppositely threaded, while the thread 18 has the same direction as the thread 17 but twice a great pitch. The thread 16 cooperates with an internally threaded sleeve 19 which guides the punch 6. In the same way the punch 7 is guided by a threaded sleeve 20 on the thread 17. The two stops 9 and 10 are guided by a threaded sleeve 21 on the thread 18.

The adjustment screw described above, with punches and stops, is used to alter the leg position, i.e. the distance between the middle lines of the legs. To alter the height of the legs the distance between the shears 2 and 3 or 4 and 5 must be altered.

The method of operation of the device will now be described with reference to FIGS. 2 5. At the start of the operation shown in FIG. 2, the strip of sheet metal is cut off at 22. This is done in the operation shown in FIG. 4. FIG. 5 shows on the left the appearance of the strip of sheet metal before it is fed forward to operation 1 in FIG. 1. The strip of metal is now fed forward towards the stop 9..Both the shears 2 and 3 cut the metal at 23 and 24 in this operation and the punches 6 and 7 make notches at 25 and 26. These are marked by thicker lines. In this operation a yoke plate 01, a side leg plate S and a yoke plate 02 are produced. After punching and notching the stop 9 is lifted, the two ready cut plates 01 and S are fed out and the stop 10 is lowered. The strip of sheet metal is then fed forward again so that the cut edge 23 meets the stop 10.

In the next operation, shown in FIG. 3, the shears 2 and 3 cut off the sheet metal at 27 and 28. A yoke plate is thus produced which differs from 01, and a side leg plate S. The stop 10 is lifted and the two ready cut plates are fed out. The stop 8 is lowered and the sheet metal fed forward to the stop.

In the third operation, shown in FIG. 4, only the shears 2 are used to cut off a blank for a central leg plate M. The stop 8 is lifted and the cut blank is fed towards the stop 11.

In the forth and last operation, shown in FIG. 5, the blank is cut to form a finished central leg plate M, the shears 4 and 5 cutting of a part of the ends of the blank.

After these four operations the five plates necessary for a plate layer in a core according to FIG. 6 have been manufactured. In the next four operations another five plates are manufactured for the next plate layer in the core according to FIG. 7.

The core is constructed of alternate layers of plates according to FIGS. 6 and 7. To show the interleaving more clearly the plate joins between yoke and leg plates in FIG. 6 are shown in broken lines in FIG. 7.

The device for cutting plates according to the invention can with advantage be combined with a device for collecting and sorting the different plates into three stacks, one for side leg plates S, one for central leg plates M and one for yoke plates 01 02 as shown in FIG. 8. In each stack alternate plates are displaced to provide the necessary overlap. The plates are coated with glue and glued together to form a stack. Each core requires five stacks of plates which are combined to a complete core when the windings have been assembled on the core legs.

Since in a working cycle comprising the four operations mentioned above, two side leg plates and two yoke plates, but only one central leg plate are produced, after a certain number of working cycles two side leg stacks, two yoke stacks and one central leg stack are obtained. The complete plate core is thus finished at the same time.

I claim:

1. Means for cutting in sequence in successive cutting stages from a strip of sheet material all the plates for the yokes and the central and outer legs of a transformer core in which the plates are interleaved with separate yoke and leg plates, which comprises a numher of shears (2,3,4,5) which are placed obliquely in relation to the feeding direction of the metal strip to cut off the plates from the metal strip, a number of punches (6,7) to make notches (25,26) in the yoke plates (01,02) for the connection of the central leg to the yoke and a number of stops (8,9,10,11) to position the metal strip as it moves forward before each cutting stage.

2. Means according to claim 1, which comprises two shears (2,3) for blank cutting, two shears (4,5 for finished cutting of the plates (M) to form the center leg and two punches (6,7) for making notches in the yoke plates for the ends of the central leg.

3. Means according to claim 1, in which the relative distances between the two shears (2,3) for the blank cutting and the relative distances between the two shears (4,5) for finishing cutting of the plates for the center leg are adjustable to determine the height of the leg.

4. Means according to claim 1, in which the two punches (6,7) for making notches in the yoke plate are adjustable with respect to each other with the help of an adjusting device comprising an adjusting screw (12) and sleeves (19,20) arranged on the adjusting screw which are joined to the punches (6,7).

5. Means according to claim 4, in which the adjusting screw also supports a sleeve (21) which guides two stops (9,10) for adjustment of the leg division.

I INITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Dated January 22, 1974 Patent No. 786, 710

In ent r( 0116 Backlin It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

In the heading, insert:

Claims priority, Application Sweden June 10, 1971, 7510/71 Signed and sealed this 17th day of September 1974.

(SEAL) Attest:

MCCOY M. GIBSON JR. C. MARSHALL DANN Attesting Officer Commissioner of Patents USCOMM-DC 60376-P69 u,s. GOVERNMENT PRINTING OFFICE: 1959 0-366-334,

FORM PO-IOSO (10-69) 

1. Means for cutting in sequence in successive cutting stages from a strip of sheet material all the plates for the yokes and the central and outer legs of a transformer core in which the plates are interleaved with separate yoke and leg plates, which comprises a number of shears (2,3,4,5) which are placed obliquely in relation to the feeding direction of the metal strip to cut off the plates from the metal strip, a number of punches (6,7) to make notches (25,26) in the yoke plates (01,02) for the connection of the central leg to the yoke and a number of stops (8,9,10,11) to position the metal strip as it moves forward before each cutting stage.
 2. Means according to claim 1, which comprises two shears (2,3) for blank cutting, two shears (4,5) for finished cutting of the plates (M) to form the center leg and two punches (6,7) for making notches in the yoke plates for the ends of the central leg.
 3. Means according to claim 1, in which the relative distances between the two shears (2,3) for the blank cutting and the relative distances between the two shears (4,5) for finishing cutting of the plates for the center leg are adjustable to determine the height of the leg.
 4. Means according to claim 1, in which the two punches (6,7) for making notches in the yoke plate are adjustable with respect to each other with the help of an adjusting device comprising an adjusting screw (12) and sleeves (19,20) arranged on the adjusting screw which are joined to the punches (6,7).
 5. Means according to claim 4, in which the adjusting screw also supports a sleeve (21) which guides two stops (9,10) for adjustment of the leg division. 